- Jason suggests Leo jump off a building and yell "Flame on!"
- When trying to snap her cabinmates out of Drew's mind control, Piper unwittingly ends up mind-controlling them herself while trying to affirm their independence. It almost sounds like she's trying to tell them that they're all individuals.
- Iris owns a shop with the acronym R.O.F.L whose workers are called ROFLcopters.
- Whilst working on the Argo II, Leo complains about the samophlange.
- The name "Perry" getting mentioned in the scene with Phineas.
- Frank mentions in Mark of Athena that he saw a TV show where they proved that Archimedes' Death Ray couldn't have worked.
- Nike apparently watches the same show. In Blood of Olympus she called Leo's bluff, saying that a TV show proved Archimedes' Death Ray couldn't have worked.
- In The Demigod Diaries Leo starts singing the theme song of Psych.
- While fighting the eidolodons, Leo says "One basketball to rule them all."
- Bacchus incorrectly refers to Jason Grace as John Green.
- Bacchus said he fought alongside Harry Cleese/Heracles/Hercules
- While steering the Argo II, Coach Hedge starts to sing the Pokémon theme song, except replacing Gotta Catch Them All with Gotta Kill Them All.
- In Mark of Athena, Tiberinus and Rhea Silvia appear as "Audrey Heburn and Gregory Peck". Percy mistakes them as the actors from Mad Men.
- Kymopoleia uses a kind of shallow pan to create sea storms. When it isn't in use, she uses its straps to wear it across her back "Captain America-style."
- While Percy and Annabeth are shrouded in the Death Mist, he thinks that he doesn't want to die looking like extras from The Walking Dead.
- Rupert Holmes' "Escape (The Piña Colada Song)" is the song playing in the elevator in The House of Hades.
- One of Leo's rejected topics for small talk is whether or not Percy saw the last episode of Doctor Who.
- When Nike orders the heroes to fight one another, Leo says that they're not going to "go Hunger Games on each other."
- Coach Hedge calls the flaming ghost of a monk "Burning Man."
- Leo calls Apollo "Music Man."
- Leo also calls Percy Aquaman.
- Leo is described as having pointed ears and at one point hears his father referred to as Vulcan. He says he doesn't like that show.
Shout Out / The Heroes of Olympus